Wheeled walking frames, known in the art as rollators, are used by individuals who require assistance in maintaining their mobility, but do not generally require a wheel chair. Rollators are commonly used by senior citizens or the disabled to support their need for mobility in normal activities both inside and outside the home. Many rollators provide a seat for users to rest on if they become tired of walking while using the rollator. These rollator seats are provided solely for the purpose of rest, and are not provided so that the user can sit on them while the rollator is moved. However, in practice, users frequently ignore express instructions not to sit and move the rollator at the same time. Users while seated typically either wheel the rollator with their feet or have another individual push the rollator for them. Since rollators are expressly not designed for this kind of use, this results in substantial risk to the seated user if the rollator wheels encounter a crack in a pavement or other obstacle which causes the rollator to unbalance and tip over. This misuse of the rollator seat has resulted in serious injuries to seated users from falling out of the unbalanced rollator; often such injuries occur to the back of the head. There is a need to prevent users from placing themselves at significant risk by sitting and being wheeled in a rollator at the same time. The present invention provides such a means through a sit-to-lock brake.